Among the Trump opponents were some protesters dressed in black and wearing masks.

The other side included self-described "patriots" and "nationalists", Trump supporters, free speech advocates, and other groups.

Daryl Tempesta, 52, who said he served in the US Air Force near the end of the Cold War, went to the rally to show his support for Mr Trump.

Image:A pro-Trump supporter bleeds after being hit by a counter protester

"As a veteran, I like the track America is on, and that Trump is willing to stand and say we are still America and we are not going to be globalist, we're not going to be a communist country," Tempesta told Reuters.

"That's a message I can get behind."

A weekly farmers market was cancelled ahead of the rally due to concerns about violence.

However, a stall selling fresh vegetables remained open for business amid the fist fighting, explosions from firecrackers and smoke.

Image:A protestor is pulled from a confrontation by a pro-Trump supporter

"We decided to show up anyway because this is our livelihood," said Tim Mueller, a farmer who owns the stall, surrounded by protesters on both sides.

At least 100 people from both camps eventually moved out of the park and continued fighting in the city's streets.

Berkeley has a long history of liberal activism and the University of California, Berkeley was a centre of protests in the 1960s.